1. Field of the Invention
The present invention relates to removable caps for writing implements, and relates in particular, to a vented removable cap adapted to allow for the flow of air therethrough while engaging the nib or writing portion of the implement to prevent the evaporation of ink therefrom.
2. Discussion of the Prior Art
Removable caps for writing implements which use ink are configured to enclose the writing or nib portion of the implement to prevent the evaporation of the ink therein as well as to protect the functional components. A conventional removable cap typically includes an outer cylindrical member having an inner cap disposed in the interior of the cylindrical member for receiving and forming an air tight seal around the writing portion of the implement. In one known type, the removable cap has a double walled construction closed at a first end and open at a second end, where the inner cap and the outer cylindrical member are integrally formed as a single unit.
Recently, it has become desirable to construct a removable cap which not only provides an adequate seal around the writing portion of an implement, but also permits air to flow axially through the interior of the cap when the cap is detached from the implement. Such removable caps typically include an outer hollow main body, an inner cap disposed within and secured to the main body, and interconnected apertures and/or spaces to establish the air passage. Examples of such configurations are described in U.S. Pat. Nos. 5,000,603 to Isoda, 5,000,604 to Isoda, GB 2220199, and PCT Application WO 89/11978.
In U.S. Pat. No. 5,000,603 to Isoda, a removable cap includes an inner cylinder positioned within an outer cylindrical body. A plurality of ribs are provided on the outer peripheral surface of the inner cylinder to secure the inner cylinder to the outer body along its mid-length, and an outer flange is provided at the open end of the inner cylinder to secure the inner cylinder to the outer cylindrical body at its bottom portion also. A complex air passageway arrangement provides communication between the inner cavity and the external atmosphere.
U.S. Pat. No. 5,000,604 to Isoda discloses an inner cylinder for covering the tip of the writing instrument secured to a double-walled outer cylinder. The inner wall of the double-walled outer cylinder is provided with a plurality of axially directed slits, and the axially directed land portions between the slits are secured to the inner cylinder. Communication between the inner cavity and the external atmosphere is provided by the axially directed slits of the inner wall of the double-walled cylindrical outer body.
British Patent Application GB 2220199 describes an outer cylindrical cap body having an inner cylinder positioned therein where the inner cylinder is secured to the outer cylinder at its open end. Air passage slots are provided adjacent the open end of the inner cylinder, and the slots are sealed by the body of the writing instrument when it is inserted into the cap. Upon removal of the body of the writing instrument, the air passage slots provide communication between the interior cavity of the cap and the outer atmosphere.
PCT Application WO 89/11978 describes a pen cap having an outer cylindrical body with an inner cylinder mounted by axially directed land portions adjacent a bore hole at the closed end of the outer cylinder.
Another known type of vented removable cap is illustrated in FIGS. 20 and 21 of the drawings. In accordance with this device, a conically shaped inner cap 100 having a plurality of axially extending ribs 102 integrally molded with the inner cap is mounted within an outer tubular member 104. Each rib 102 possesses a groove 106 which locks with an annular rib 108 formed on the inner surface of the outer tubular member to effect the mounting. The axial extending ribs 102 directly abut the inner peripheral surface of the outer tubular member, and outer tubular member 104 also possesses raised portions 110 which are in contact with the peripheral surface of the inner cap. Air passage slots are provided between the axial ribs of the inner cap.
Although these caps are effective in sealing the writing portion of the implement and also incorporate provisions to enable external air to flow through the interior of the cap when the cap is detached from the implement, these devices present a number of disadvantages. For example, each cap includes an inherently complex design, specifically with regard to the mounting of the inner cap to the main cap body which requires close tolerances during construction to prevent obstruction of the vent openings. Furthermore, the inner caps of these devices are supported by the main cap bodies along a substantial portion of the peripheral surfaces of the inner caps, such that any pivotal movement of the inner cap relative to the main cap body is minimized or eliminated, requiring precise molding and constructional tolerances. Consequently, if the inner cap is assembled in non-axial alignment relative to the main cap body, which may occur due to the precision in which the component parts are manufactured, the inner cap is not capable of adjusting its position relative to the main cap body to receive the writing portion of the implement.